Salinity

ODF analyzes salinity via a conductivity measurement, both onshore and at sea. Contact Susan Becker for details and pricing.

The methods below are compatible with those described in the oxygen section of the GO-SHIP repeat hydrography manual (Kawano, 2010). 

Sampling Procedures

The salinity samples are collected in 200 ml Kimax high-alumina borosilicate bottles that are rinsed at least three times with sample water prior to filling.
The bottles are sealed with custom-made plastic insert thimbles and Nalgene screw caps. 

Equipment and Techniques

Salinity measurements are made using a Guildline Autosal 8400A or 8400B salinometer interfaced to a PC using LabView software developed by ODF. Water bath temperature is adjustable and set within 1-2ºC of lab temperature. Salinity analyses are performed after samples equilibrate to laboratory temperature range, usually 12 hours after collection while at sea or the next day for shore based analysis. 

Data Processing

PSS-78 salinity (UNESCO, 1981) is calculated for each sample from the measured conductivity ratios. The offset between the initial standard seawater value and its reference value is applied to each sample. Then the difference (if any) between the initial and final vials of standard seawater is applied to each sample as a linear function of elapsed run time.

Standards

Standardization is preformed with P-series IAPSO standard seawater. The salinometer is standardized for each group of samples analyzed (1 or 2 casts, up to 72 samples) using two bottles of standard seawater: one at the beginning and end of each set of measurements.

References

Kawano, T. "Method for Salinity (Conductivity Ratio) Measurement," IOCCP Report No. 14, GO-SHIP Repeat Hydrography Manual: A Collection of Expert Reports and Guidelines, ICPO Publication Series No.134 v.1 (2010).

UNESCO, "Background papers and supporting data on the Practical Salinity Scale, 1978," UNESCO Technical Papers in Marine Science, No. 37 144 (1981).